1. Field of the Invention
The present invention relates to a dual damascene process, in particular, to a simplified dual damascene process, in which the steps of stacking the dielectric layer, the etch stop layer, and the stack dielectric layer in the conventional process are omitted and the dielectric constant of the inter-metal dielectric (IMD) is reduced, thereby obtaining a simplified dual damascene process with good trench profile.
2. Description of the Prior Art
As the lines of IC design in semiconductor processing become more and more highly concentrated, the unit area bears a larger and larger current. Since copper has both a low resistance and a high anti-electromigration resistance ability, conventional aluminum interconnect processing is substituted with copper interconnect processing.
When copper is used as the material of the interconnects, the step of patterning the copper interconnects is not easily performed using the current etching technology because the steam pressure of a halide of copper is not high enough. Therefore, a dual damascene process is used to finish both the copper interconnect and the copper plug.
The main advantage of the dual damascene process is that it can be used for etching and filling the conductive metal. There are two method of fabricating the trench having the dual damascene structure. Refer to FIG. 1 which is a cross-sectional diagram of a first dual damascene process according to the prior art. When etching the via 44 of the lower dielectric layer 38 and the trench 46 of dielectric layer 42, a SiN layer is used as a first etch stopping layer 40. The inter-metal dielectric (IMD) with a high dielectric constant (k) used, becomes one problem for using SiN as a first etch stopping layer 40. Also, the capacitance of the dielectric layer increases, resulting in poor isolation of the dielectric layer.
Another dual damascene process of the prior art is shown in FIG. 2. When the trench 46 and the via 44 are etched without using any etch stop layer, it is difficult to control the trench profile and the deepness.
Therefore, the present invention provides a simplified dual damascene process, which reduces the dielectric constant of the inter-metal dielectric (IMD) and shortens the processing time of the dual damascene process and furthermore obtains a better trench profile.